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##

Software Availability

There are several pieces of software available for subspace
iteration described in this section.
EB12 is a routine by Duff and Scott for subspace
iteration [143]. It is part of the Harwell Subroutine
Library. Given a real unsymmetric matrix, this routine
computes the eigenvalues that have the largest positive
real part, the largest (in modulus) negative real part, or the largest
modulus, with the option of returning the associated
eigenvectors. It can also be used to compute other
eigenvalues.

SRRIT is a package by Bai and Stewart for calculating a few
eigenvalues with largest modulus for a real nonsymmetric
matrix [37]. It also computes an approximate
orthonormal basis for the associated invariant
subspace. SRRIT is nonproprietary. The template in
§7.4.3 is closely modeled on SRRIT.

LOPSI is a package by Stewart and Jennings that uses
subspace iteration combined with an oblique projection to
compute a few eigenvalues of largest modulus and the
corresponding eigenvectors of a large sparse
matrix [427]. However, LOPSI is based on eigendecompositions
instead of the Schur form, and hence one may expect less
accuracy in LOPSI than in SRRIT, especially for
ill-conditioned eigenvalue problems.

For more information about this software including how to access
it, see the book's homepage ETHOME.

** Next:** Arnoldi Method Y. Saad
** Up:** Single- and Multiple-Vector Iterations
** Previous:** Subspace Iteration
** Contents**
** Index**
Susan Blackford
2000-11-20